Things That Google Knows About You
Obviously if you use are a user of Google services you are sharing a lot of your search behavior among other things with Google as well. The E-Justice blog has published an interesting post on 25 Surprising Things That Google Knows About You. Below is a sample from the complete list of 25.

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The web pages you visit: Google AdSense is used by many web pages for online advertising, and Google’s cookies record your visits to web pages with their ad program on them.
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The blogs you read: If you use Google Reader, Google knows the blogs you subscribe to. Even if you’re not on Google Reader, Google knows all of the Blogger pages you visit.
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Who and what you’re emailing: GMail users, and those who send mail to GMail users share a variety of personal and business information with Google.
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What’s on your PC: If you’re using Google Desktop, Google knows everything that you keep on your computer.
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Your schedule: Google Calendar opens your personal and business schedule up to the prying eyes of Google.
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Your social network and interests: Google indexes sites like Orkut, Facebook, and Digg, and as such, has access to information about what you’re interested in online.
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Where you and your friends are: Using Google Latitude, cell phone users can share their location with others. Even if you’re not using Latitude, Google Maps for mobile can approximate your location.
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Your medical issues: Do you use Google Health? If so, you’re sharing your entire medical history with Google.
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Mobile number: On SMS, Google Mobile, and Gmail, you can reveal your mobile number to Google.
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What you, your friends and family look like and do: With the photo editor Picasa, you’re revealing your photographs, friends, and moments to Google.
SEO TRICKS GUIDE (http://seotricksguide.info/2009/03/things-that-google-knows-about-you/)